Dynamic Changes of QT Dispersion as a Predictor of Myocardial Ischemia on Exercise Testing in Patients with Angina Pectoris.

Abstract

The difference between the maximum and minimum QT intervals on the standard 12-lead ECG (QT dispersion) may be a significant predictor of serious arrhythmias. Dynamic changes in QTd were determined during exercise-induced ischemia in 15 patients with effort angina (> or = 75% coronary stenosis) and 10 normal individuals. Treadmill exercise testing was performed according to Bruce's protocol and the rate-corrected QT dispersion (QTcd) was calculated using Bazett's formula. The resting QTcd before exercise was similar in the angina patients and the controls. After the first stage of exercise, QTcd was significantly increased in the angina patients (p = 0.035), while it remained near baseline in the controls. Five minutes after completing exercise, QTcd was significantly greater in the angina patients than in the controls (p = 0.011). Furthermore, QTcd values after the first stage of exercise were significantly correlated with the maximum ST depression observed on completing exercise in the angina patients (r = 0.714, p = 0.0028). Because QTd may represent the heterogeneity of ventricular repolarization, its significant exercise-induced increase in the angina patients suggests that myocardial ischemia caused repolarization disorders. The significant correlation between QTcd values after the first stage of exercise (before significant ST depression) and the maximum ST depression on completing exercise suggests that an increase in QTcd preceding ischemic ST depression may predict myocardial ischemia. In addition, even daily activities not causing significant ST changes may increase QTcd and the risk of serious arrhythmia in angina patients.

Prolongation of the QT-corrected interval during dobutamine stress echocardiography: a marker for ischemia

“…A 12-lead ECG is currently used as a complementary tool to diagnose ischemia during dobutamine stress ECG but it has not been conclusively shown that deviations in the ST segment are reliable markers for ischemia [10,11]. As noted in this study, there are a number of false-negative and false-positive results obtained during exercise or pharmacological stress testing if ST-T changes on the ECG are considered to document an ischemic response, especially in women.…”

“…Thus, increase in QTc interval, as a marker of ischemia, is a simple, useful parameter that can improve the sensitivity and specificity of dobutamine stress tests using an ECG alone. A number of studies have evaluated the role of QTc interval and QT dispersion in myocardial ischemia and as a marker of arrhythmic events [10][11][12][13]. We along with others have shown an association between QT prolongation and ischemia during exercise stress testing [5,11].…”

QT Dispersion in Patients with Polycystic Ovary Syndrome.

“…Recently, several studies reported that QT dispersion after exercise was a more powerful predictor of coronary artery disease than QT dispersion at rest. 18,19) Koide, et al reported that QT dispersion immediately after exercise was a clinically useful indicator of significant coronary stenosis independent of gender or the presence or absence of exercise-induced significant ST-segment depression. 18) They found that QT dispersion immediately after exercise was significantly more sensitive in men and significantly more specific in women than exercise-induced significant ST-segment depression as an indicator of significant coronary stenosis.…”

Changes during exercise of ECG intervals related to increased risk for ventricular arrhythmia in repaired tetralogy of Fallot and their relationship to right ventricular size and function

“…Compared to controls a larger dispersion of ventricular repolarisation was found in patients with ventricular tachycardia/fibrillation [29]. QTc dispersion increased during exercise in patients with angina pectoris as well as in patients with isolated myocardial bridging [31,32], while no change or a decrease was seen in healthy controls [30][31][32]. In chronic heart failure a larger QTc dispersion predicted SCD [27].…”